全文获取类型
| 收费全文 | 4081篇 |
| 免费 | 61篇 |
专业分类
| 4142篇 |
出版年
| 2020年 | 62篇 |
| 2019年 | 78篇 |
| 2018年 | 111篇 |
| 2017年 | 125篇 |
| 2016年 | 124篇 |
| 2015年 | 75篇 |
| 2014年 | 87篇 |
| 2013年 | 1349篇 |
| 2012年 | 115篇 |
| 2011年 | 99篇 |
| 2010年 | 104篇 |
| 2009年 | 99篇 |
| 2008年 | 85篇 |
| 2007年 | 80篇 |
| 2006年 | 61篇 |
| 2005年 | 43篇 |
| 2004年 | 60篇 |
| 2003年 | 63篇 |
| 2002年 | 45篇 |
| 2001年 | 45篇 |
| 2000年 | 34篇 |
| 1999年 | 49篇 |
| 1998年 | 32篇 |
| 1997年 | 36篇 |
| 1996年 | 28篇 |
| 1995年 | 35篇 |
| 1994年 | 32篇 |
| 1993年 | 26篇 |
| 1992年 | 30篇 |
| 1991年 | 28篇 |
| 1990年 | 26篇 |
| 1989年 | 29篇 |
| 1987年 | 26篇 |
| 1986年 | 31篇 |
| 1985年 | 31篇 |
| 1984年 | 40篇 |
| 1983年 | 36篇 |
| 1982年 | 29篇 |
| 1981年 | 32篇 |
| 1980年 | 38篇 |
| 1979年 | 45篇 |
| 1978年 | 35篇 |
| 1977年 | 35篇 |
| 1976年 | 31篇 |
| 1975年 | 34篇 |
| 1974年 | 32篇 |
| 1973年 | 39篇 |
| 1972年 | 25篇 |
| 1971年 | 32篇 |
| 1969年 | 27篇 |
排序方式： 共有4142条查询结果，搜索用时 0 毫秒
71.
72.
73.
74.
75.
F.R. Bridge 《国际历史评论》2016,38(2):264-274
ABSTRACTAlthough in terms of their bilateral relations the ‘traditional friendship’ between Great Britain and Austria-Hungary was no mere phrase, in general political terms British policy in the last decade before the War was characterised by Grey's determination to cultivate the ententes with France and Russia and to do nothing to upset that division of Europe into two balancing groups (with Austria-Hungary firmly in the German camp) which he saw as the best guarantee of peace. Even though the Austrians gradually recovered from the shock of the Bosnian Crisis, in which Grey had come forward against them as Russia's chief supporter, and though the British for their part came to see in Austria-Hungary a useful element of stability in the Near East, Grey's attempts to uphold the unity of the Concert in the Balkan Wars were in the end vitiated by his overriding concern to avoid offending his Entente partners. Indeed, as the crisis deepened in the last year of peace, he took refuge in an increasingly abstentionist attitude, the objective effect of which - and herein, it is here argued, lies Grey's responsibility - was to intensify Vienna's desperation and loss of faith in the Concert that soon proved fatal to peace. 相似文献
76.
F.E. Freeks 《SJOT: Scandinavian Journal of the Old Testament》2016,30(2):236-248
This article explored the possible role of a “mentor” and is based on theoretical pointers from the Old Testament figures. Throughout the article mentoring was explored according to the approach of (T. Van der Walt:2007, 309). The background and narratives of Old Testament figures such as Abraham, Isaac, Jacob, Joseph, Moses, Joshua, Elijah, Elisha, David and Solomon were investigated. They were chosen for their leadership and guidance. Abraham and Jacob were the patriarchs of the Bible. Moses was and is still recognized as the greatest leader in history. Elijah and David were great and mighty prophets and kings. These narratives linked with the theory about mentoring and the significance thereof in today’s society of a father as mentor in a home. 相似文献
77.
The quantitative assessment of COH fluids is crucial in modeling geological processes. The composition of fluids, and in particular their H2O/CO2 ratio, can influence the melting temperatures, the location of hydration or carbonation reactions, and the solute transport capability in several rock systems. In the scientific literature, COH fluids speciation has been generally assumed on the basis of thermodynamic calculations using equations of state of simple H2O–nonpolar gas systems (e.g., H2O–CO2–CH4). Only few authors dealt with the experimental determination of high‐pressure COH fluid species at different conditions, using diverse experimental and analytical approaches (e.g., piston cylinder + capsule piercing + gas chromatography/mass spectrometry; cold seal + silica glass capsules + Raman). In this contribution, we present a new methodology for the synthesis and the analysis of COH fluids in experimental capsules, which allows the quantitative determination of volatiles in the fluid by means of a capsule‐piercing device connected to a quadrupole mass spectrometer. COH fluids are synthesized starting from oxalic acid dihydrate at P = amb and T = 250°C in single capsules heated in a furnace, and at P = 1 GPa and T = 800°C using a piston‐cylinder apparatus and the double‐capsule technique to control the redox conditions employing the rhenium–rhenium oxide oxygen buffer. A quantitative analysis of H2O, CO2, CH4, CO, H2, O2, and N2 along with associated statistical errors is obtained by linear regression of the m/z data of the sample and of standard gas mixtures of known composition. The estimated uncertainties are typically <1% for H2O and CO2, and <5% for CO. Our results suggest that the COH fluid speciation is preserved during and after quench, as the experimental data closely mimic the thermodynamic model both in terms of bulk composition and fluid speciation. 相似文献
78.
Mineral precipitation in an open fracture plays a crucial role in the evolution of fracture permeability in rocks, and the microstructural development and precipitation rates are closely linked to fluid composition, the kind of host rock as well as temperature and pressure. In this study, we develop a continuum thermodynamic model to understand polycrystalline growth of quartz aggregates from the rock surface. The adapted multiphase‐field model takes into consideration both the absolute growth rate as a function of the driving force of the reaction (free energy differences between solid and liquid phases), and the equilibrium crystal shape (Wulff shape). In addition, we realize the anisotropic shape of the quartz crystal by introducing relative growth rates of the facets. The missing parameters of the model, including surface energy and relative growth rates, are determined by detailed analysis of the crystal shapes and crystallographic orientation of polycrystalline quartz aggregates in veins synthesized in previous hydrothermal experiments. The growth simulations were carried out for a single crystal and for grain aggregates from a rock surface. The single crystal simulation reveals the importance of crystal facetting on the growth rate; for example, growth velocity in the c‐axis direction drops by a factor of ~9 when the faceting is complete. The textures produced by the polycrystal simulations are similar to those observed in the hydrothermal experiments, including the number of surviving grains and crystallographic preferred orientations as a function of the distance from the rock wall. Our model and the methods to define its parameters provide a basis for further investigation of fracture sealing under varying conditions. 相似文献
79.
Highly saline, deep‐seated basement brines are of major importance for ore‐forming processes, but their genesis is controversial. Based on studies of fluid inclusions from hydrothermal veins of various ages, we reconstruct the temporal evolution of continental basement fluids from the Variscan Schwarzwald (Germany). During the Carboniferous (vein type i), quartz–tourmaline veins precipitated from low‐salinity (<4.5wt% NaCl + CaCl2), high‐temperature (≤390°C) H2O‐NaCl‐(CO2‐CH4) fluids with Cl/Br mass ratios = 50–146. In the Permian (vein type ii), cooling of H2O‐NaCl‐(KCl‐CaCl2) metamorphic fluids (T ≤ 310°C, 2–4.5wt% NaCl + CaCl2, Cl/Br mass ratios = 90) leads to the precipitation of quartz‐Sb‐Au veins. Around the Triassic–Jurassic boundary (vein type iii), quartz–haematite veins formed from two distinct fluids: a low‐salinity fluid (similar to (ii)) and a high‐salinity fluid (T = 100–320°C, >20wt% NaCl + CaCl2, Cl/Br mass ratios = 60–110). Both fluids types were present during vein formation but did not mix with each other (because of hydrogeological reasons). Jurassic–Cretaceous veins (vein type iv) record fluid mixing between an older bittern brine (Cl/Br mass ratios ~80) and a younger halite dissolution brine (Cl/Br mass ratios >1000) of similar salinity, resulting in a mixed H2O‐NaCl‐CaCl2 brine (50–140°C, 23–26wt% NaCl + CaCl2, Cl/Br mass ratios = 80–520). During post‐Cretaceous times (vein type v), the opening of the Upper Rhine Graben and the concomitant juxtaposition of various aquifers, which enabled mixing of high‐ and low‐salinity fluids and resulted in vein formation (multicomponent fluid H2O‐NaCl‐CaCl2‐(SO4‐HCO3), 70–190°C, 5–25wt% NaCl‐CaCl2 and Cl/Br mass ratios = 2–140). The first occurrence of highly saline brines is recorded in veins that formed shortly after deposition of halite in the Muschelkalk Ocean above the basement, suggesting an external source of the brine's salinity. Hence, today's brines in the European basement probably developed from inherited evaporitic bittern brines. These were afterwards extensively modified by fluid–rock interaction on their migration paths through the crystalline basement and later by mixing with younger meteoric fluids and halite dissolution brines. 相似文献
80.
Thomas P. Narins 《Geography Compass》2016,10(7):283-292
Since the early 2000s, when China joined the World Trade Organization and the Chinese government announced an official ‘going out policy’ to encourage economic engagement beyond China's territorial borders, growth of Chinese foreign direct investment (FDI) and trade with both Africa and Latin America has risen exponentially. Reasons for this rise include (1) Chinese economic actors' view that expansion within these former European colonial regions is critical for accessing primary resources and new markets and (2) leadership in Beijing's view that its legitimacy continues to be based on economic growth. Given China's recent bleak economic forecast and plunging stock market, an increase in Chinese overseas economic engagement in Africa and Latin America warrants a closer examination of the ‘Chinese model’ of economic expansion in the developing world and implies that the Chinese economy may be more dependent on connections with these regions than has been previously suggested. By distinguishing the political economic forces at play, on the ground, in Africa from those in Latin America, Chinese economic engagement tactics in these regions can be more accurately understood as a set of dependent and negotiated processes that are location specific. 相似文献